1. Field of the Invention
The present invention relates to a microchannel plate, as one of secondary-electron multiplying means, and a method for manufacturing the same.
2. Description of the Prior Art
Microchannel plates, having fine perforations called microchannels, are used for secondary electron multiplication.
FIG. 1 shows an image intensifying system using a microchannel plate. As shown in FIG. 1, photoelectrons 3 emitted from photocathode 2, excited by incident light 1, are accelerated by voltage E1, applied between cathode 2 and first accelerating electrode 6a of microchannel plate 4, and are then projected diagonally on microchannels 5.
A secondary-electron emission surface is formed inside microchannels 5. Secondary electrons emitted from the emission surface are accelerated by voltage E2, applied between first and second electrodes 6a and 6b on two opposite sides of microchannel plate 4. Then, the electrons repeat collisions inside each microchannel, as shown in FIG. 2. Multiplied secondary electrons 7, delivered from plate 4 in this manner, are projected on anode-cum-fluorescent screen 8 by voltage E3, thus forming a visible image.
Prior art microchannel plates generally comprise a bundle of capillary glass tubes, for use as microchannels, each having an inside diameter of about 15 .mu.m and length of about 1.5 mm. A secondary-electron emission surface made of PbO is formed on the inner surface of each capillary tube.
These conventional microchannel plates are manufactured as follows. First, cylindrical glass bodies to be used as capillary tubes, each having a core therein, are each heated and extended into individual elongate bodies. Then, a number of such elongate bodies are bundled and fused together. After they are heated and extended again, the elongate bodies are fused to be united in an integrated body. The resultant integral structure is sliced and ground, and the core portion is removed by etching. PbO is formed on the inner surface of each capillary tube by heat treatment. Thereafter, accelerating electrodes are formed by vacuum evaporation.
According to this manufacturing method, the unification of the individual capillary tubes, as well as the formation thereof, requires complicated processes. Thus, the conventional method is low in productivity, and entails high cost. Moreover, a great number of capillary tubes must be provided for microchannel plates of a wide area, resulting in lower productivity. Since the way of bundling the capillary tubes is subject to restriction, furthermore, the microchannel plates cannot readily be varied in shape.
Thus, the prior art microchannel plates require sophisticated manufacturing processes, and can hardly enjoy a wide-area configuration or variation in shape.